When WiFi doesn’t go far enough, and LoRa is going to break the bank, there’s always the wonderful world of ISM band radios! The SympleLink radio system from Raging Bits might just be what you’re looking for. Unlike the super cheap ISM devices that send a single UART stream, the SympleLink has firmware which can handle a UART, an I2C bus, and 4 GPIO! That’s enough to control just about anything on the receiving end.
Each device has a unique address, and will only connect and communicate with its associated central device. The devices are capable of up to a 1/2 mile (800m) transmission distance if line-of-sight is possible. A single Central module can communicate with many Peripheral boards, and the included documentation is quite detailed and will have you up and running in no time.
The SympleLink uses the LPD433 band, which means that it’s only legal to use in Europe and Malaysia as an ISM band device; licensed amateur radio operators may be able to use these devices if they comply with all the important regulations (including transmitting your callsign) but it’s best to check the laws in your country.
